Sunday, August 26, 2007

Did maternal mortality rise in 2004?

Yesterday, MSNBC blared the headline, More US women dying in childbirth. According to the accompanying article:
U.S. women are dying from childbirth at the highest rate in decades, new government figures show. Though the risk of death is very small, experts believe increasing maternal obesity and a jump in Caesarean sections are partly to blame.
Not exactly. Indeed, the article itself acknowledges:
Some numbers crunchers note that a change in how such deaths are reported also may be a factor.
The National Center for Health Statistics provides comprehensive documentation for death rates, so we can look at the actual data ourselves, to see if the headlines are justified. Let's look first at the definitions of maternal death. In February 2007, the CDC published Maternal Mortality and Related Concepts:
"Maternal deaths" are defined by the World Health Organization as "the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes..."
"Direct obstetric deaths: those resulting from obstetric complications of the pregnant state (pregnancy, labour and puerperium), from interventions, omissions, incorrect treatment, or from a chain of events resulting from any of the above."
"Indirect obstetric deaths: those resulting from previous existing disease or disease that developed during pregnancy and which was not due to direct obstetric causes, but which was aggravated by physiologic effects of pregnancy."
Now let's look at the data for 2004 as compared to the data for 2003. The first thing you notice is that the absolute number of deaths rose from 495 to 540 deaths, an increase of 45 deaths. Yet a closer look reveals that direct obstetric deaths have changed very little. There were 473 direct maternal deaths in 2003, and 492 direct maternal deaths in 2004, an increase of only 19 deaths. The rate for direct maternal deaths rose from 9.3/100,000 to 9.6/100,000, a change that may not even be statistical significant.

The bulk of the change from 2003 to 2004 occured in two area. There was a large increase in deaths from indirect maternal causes (pre-existing disease aggravated by pregnancy) and deaths from maternal causes more than 42 days after delivery or pregnancy termination. These increases could be real, or they could merely reflect the fact that death certificates now have additional questions on them that are designed specifically to identify late maternal deaths.

Even if these increases are real, they may simply be a result of the increasing age of pregnant women, and the increasing rate of multiple births associated with fertility treatments. According to Births: Final Data for 2004:
The birth rate for women aged 35–39 years was ... up 4 percent from the rate in 2003. The rate for this age group ... has risen 43 percent since only 1990... From 1990 to 2004, the number of births to this age group rose by 50 percent, compared with a 5-percent increase in the population of women aged 35–39 years.

Women in their forties—In 2004, the birth rate for women aged 40–44 years rose to 8.9 births per 1,000 women .., an increase of 2 percent... Since 1981, the rate for this age group has generally increased and has risen 62 percent since 1990. The number of births to women aged 40–44 years increased by 3 percent during 2003–04, from 101,005 to 103,769, more than twice the number reported for 1990 and the highest number on record for the United States; the population of women aged 40–44 years increased only slightly (by less than 1 percent from 2003 to 2004). The birth rate for women aged 45–49 years was unchanged between 2003 and 2004, at 0.5 births per 1,000 women. This rate more than doubled between 1990 and 2000 but has remained stable since. The number of births to women aged 45–49 years increased 4 percent, from 5,522 to 5,748 between 2003 and 2004, more than three times the number for 1990 ...

Births to women aged 50 years and over—The number of births to women aged 50–54 years increased from 323 to 374 for 2003–04. The number of births to women in this age group has increased dramatically from 144 in 1997,..

The increase in birth rates for women 35 years of age and over during the last 20 years has been linked, in part, to the use of fertility-enhancing therapies... In 2004, 1 out of 18 births to women aged 35 years and over was in a multiple delivery, an outcome associated with infertility treatment, compared with 1 out of 33 births to women under 35 years of age. The incidence of multiple deliveries dramatically increases with the age of mother; for example, one out of five births to women aged 45–49 years and one out of every two births to women aged 50–54 years was a multiple birth in 2004.
The bottom line is that it is unclear whether there has even been an increase in maternal deaths; we may simply be seeing an increase in the reporting of maternal deaths, particularly those that occur long after the delivery. Second, the overall increase in the age of pregnant women, and therefore the pre-existing health problems of pregnant women, may account for any increase in the rate of maternal deaths. As the age of pregnant women increases, and particularly as the number of perimenopausal or postmenopausal pregnant women increases, we should expect to see an increase in the maternal mortality rate. This does not reflect a problem with obstetric care, but rather the increased risk associated with pregnancies of women 45-54.


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